“Some places now have a law that requires fast food restaurants to label each item with how many calories it has.”

You're having a conversation with a friend from another country. You're talking about fast food and how unhealthy it is. You mention something that you've seen in fast food restaurants in some cities that you've traveled to.

Some places now have a law that requires fast food restaurants to label each item with how many calories it has.

"Fast food" restaurants are places where you can get cheap food quickly. In the U.S., hamburgers are the most common fast food. There are also fast food restaurants for tacos, fried chicken, and sandwiches.

You can talk about the food itself as "fast food":

I try not to eat too much fast food.

Or you can talk about the restauraunts that sell fast food:

There sure are a lot of fast food places around here!

If I'm on a road trip, I usually just stop and eat at a fast food restaurant.

"Calories" are a measurement of the amount of energy that's in food. Some food items are labeled with the number of calories. People who are trying to lose or gain weight might discuss how many calories different kinds of food have.